Genetic Identification of Dematiaceous Fungi Isolated from Washing Machine in Japan, and Considering of Fungal Removal Methods

Abstract

In 2017, 2 household washing machines which were used at a house in Saitama prefecture were tested for fungal flora sampling. The fungi were identified in detail via genetic analysis of the ITS region. The number of fungi which were isolated were 8.7 10 6 6.1 10 7 cfu/100cm 2 and dematiaceous fungi such as Ochroconis musae, Exophiala, Cyphellophora, Knufia epidermidis were dominant. As for Knufia epidermidis, this is the first report for identification from a Japanese household. The number of isolated Cladosporium, which is common in the environment, was fewer compared with the above 4 genera. The identified fungi were Cladosporium halatolerans, which is recently being recognized as the main species of Cladosporium. In our research, we have cleaned the 2 washing machines with different bleaches. Residual fungi was detected in washing machine A, which was cleaned with an oxygen bleach. On the other hand, no fungi was detected in washing machine B, which was cleaned with a chlorine bleach.

Evaluation of building washing machines as an extreme environment for potentially pathogenic fungi

“…These fungi are characterized by their visible dark pigmentation on plates, attributed to melanin, and were confirmed through molecular sequencing methods. The black fungi isolated in this study have the potential to cause subcutaneous phaeohyphomycosis diseases, particularly in individuals with compromised immune systems 23,24 . Within the black fungus group, the genus Ochroconis (9%) was the most commonly isolated.…”

Isolation of <i>Simplicillium sympodiophorum</i> and <i>Toxicocladosporium irritans</i> from the Blowout Air of Household Air Conditioners

“…When large numbers of colonies of the same species presumed to be major contaminated fungi were isolated, and one strain per one AC was extracted and stored. Stock cultures of fungi were identified by nuclear ribosomal internal transcribed spacer (ITS) region analysis, as described by Hashimoto et al (2019) . Molecular phylogenetic analysis was conducted in MEGA X (Kumar et al, 2018) .…”

“…Abe (1998) demonstrated that inside of ACs were high humidity environment where hygrophilous fungi can grow easily. However, since S. sympodiophorum and T. irritans are not isolated in bathrooms and washing machines containing much moisture (Hamada and Abe, 2008;Hashimoto et al, 2019) , it cannot conclude that they are likely to grow if the humidity is simply high. Although bedding, which exist in the same environment (bedrooms) as ACs, are also contamination sources of fungi, S. sympodiophorum and T. irritans are not isolated, probably because of relatively low in water (Hashimoto et al, 2020) .…”